Our objective is to achieve a major advance in the technology used to assess disability in children and youth. Measurement and practical requirements for identifying disability and evaluating individual progress across pediatric age groups and care settings present a serious dilemma to current fixed-item survey instruments. We have developed a prototype computerized, adaptive application called PEDI-CAT that produces comparable scoring levels, precision, and responsiveness to change at significant reductions in respondent burden compared to full-length version of Pediatric Evaluation of Disability Inventory (PEDI) scales. Phase II work will improve the PEDI item pool by broadening the appropriate age range measured by each scale. Norm-based item calibrations for the PEDI functional scales (mobility, self-care, and social functioning) will be developed by collecting general population data for the new PEDI. Scoring algorithms and score reports will be created for a fully operational PEDI-CAT system. The full PEDI-CAT will be evaluated in terms of reliability, validity, and precision across score levels to create an operational system for the assessment of disability in children and youth that will improve measurement in clinical research and practice. Specific aims are to: 1. Expand the original PEDI item pool in mobility, self-care and social functioning to incorporate functional tasks appropriate for children to 14 years of age; evaluate new items through content expert feedback, cognitive testing in parent and clinician focus groups, and a small field study (N=100). 2. Develop final item calibrations and normative profiles for the revised functioning item pools by collecting responses from two large, nationally-representative samples of caretakers for children age 6 months to 14 years: 1) a telephone-based survey sample (N=840); and 2) a web-based survey sample (N=1400). Estimate the extent to which data collection method (internet vs. telephone) is associated with differential item functioning. 3. Create a fully operational PEDI-CAT system with norm-based scoring and interpretive reports that can be administered on multiple platforms (e.g., desktop, hand-held devices); demonstrate the accuracy, precision, and reductions in respondent burden of the PEDI-CAT through real data simulation studies. 4. Confirm the validity and respondent acceptance of the PEDI-CAT in a clinical sample of children known to differ in disability status: receiving rehabilitation services (N=50) vs. not (N=50). A practical and feasible PEDI-CAT will greatly improve the information used in making decisions about disability status, service eligibility, program needs, outcomes of rehabilitation interventions and in clinical research. This new disability assessment will fill a critical void with a system that is more practical and precise, programmed to be fully operational on both desktop and hand-held devices.